The present invention relates to hydraulic fracturing treatments. More particularly, the present invention relates to methods and compositions for carrier fluids comprising water-absorbent fibers.
Servicing fluids comprising suspended or slurried particulates are used in a variety of operations and treatments performed in oil and gas wells. Such operations and treatments include, but are not limited to, well completion operations such as fracturing, gravel packing, and frac-packing.
An example of a production stimulation operation using a servicing fluid having particles suspended therein is hydraulic fracturing. That is, a type of servicing fluid referred to in the art as a fracturing fluid is pumped through a well bore into a subterranean zone to be stimulated at a rate and pressure such that fractures are formed and extended into the subterranean zone. The fracture or fractures may be horizontal or vertical, with the latter usually predominating, and with the tendency toward vertical fractures generally increasing with the depth of the formation being fractured. Generally, fracturing fluids are viscous fluids in the form of gels, emulsions, or foams. The particulate materials used in these operations are often referred to as proppant. The proppant is deposited in the fracture and functions, inter alia, to maintain the integrity of the fracture open while maintaining conductive channels through which such produced fluids can flow upon completion of the fracturing treatment and release of the attendant hydraulic pressure.
Suspended or slurried particulates also are used in well completion operations such as gravel packing. Gravel packing treatments are used, inter alia, to reduce the migration of unconsolidated formation particulates into the well bore. In gravel packing operations, particulates, often referred to in the art as gravel, are carried to a well bore in a subterranean producing zone by a servicing fluid that acts as a gravel carrier fluid. That is, the particulates are suspended in a carrier fluid, which may be and usually is viscosified, and the carrier fluid is pumped into a well bore in which the gravel pack is to be placed. As the particulates are placed in or near the zone, the carrier fluid leaks off into the subterranean zone and/or is returned to the surface. The resultant gravel pack acts as a sort of filter to prevent the production of the formation solids with the produced fluids. Traditional gravel pack operations involve placing a gravel pack screen in the well bore before packing the surrounding annulus between the screen and the well bore with gravel. The gravel pack screen is generally a filter assembly used to support and retain the gravel placed during the gravel pack operation. A wide range of sizes and screen configurations is available to suit the characteristics of a well bore, the production fluid, and any particulates in the subterranean formation. Gravel packs are used, among other reasons, to stabilize the formation while causing minimal impairment to well productivity.
In some situations, hydraulic fracturing and gravel packing operations may be combined into a single treatment. Such treatments are often referred to as “frac pack” operations. In some cases, the treatments are completed with a gravel pack screen assembly in place with the hydraulic fracturing treatment being pumped through the annular space between the casing and screen. In this situation, the hydraulic fracturing treatment ends in a screen-out condition, creating an annular gravel pack between the screen and casing. In other cases, the fracturing treatment may be performed prior to installing the screen and placing a gravel pack.
Previously, fibrous, non-degradable materials, such as glass, aramide, nylon, ceramic, and metal, have been added to carrier fluids to help decrease, or eliminate, the flowback of proppant both during and after the fracturing treatment. In addition to decreasing proppant flowback, these fluids also offered the additional benefits of decreasing the required polymer loadings of viscosifier and lowering the amount of fluid loss during the fracturing treatment. Unfortunately, many of these fluids exhibit limited usefulness, due ate least in part to the fact that after the placement of proppant inside the fracture, the fibers remain within the proppant pack, plugging the pore spaces between the proppant particulate, and causing the fracture conductivity to be significantly diminished under closure stresses.
One area where degradable fibers are commonly used is in the field of disposable absorbent products. Water-absorbent degradable fibers have been used in a variety of applications, including disposable diapers, feminine hygiene products, surgical drapes, and wound dressings. These materials retain their integrity and strength during use, but after such use, may be disposed of more efficiently. Such products typically use woven fibers, and, to date, have not been subjected to widespread use in the oilfield industry.